The aim of this study was to develop self-emulsifying system to improve the dissolution of Passiflora foetida extract and evaluate its stability. The formulations studied were composed of Captex 200, Captex 300 or ethyl oleate as oils, Tween 80 and/or Cremophor EL as surfactants, propylene glycol or polyethylene glycol 400 as co-solvents. Dissolution in water, 0.1 N HCl and pH 6.8 phosphate buffer, and stability of the extract in the self-emulsifying systems at varied storage conditions, were investigated by monitoring the amount of vitexin, total flavonoids and total phenolic compounds. The results showed that the self-emulsifying systems could be obtained with surfactant concentrations between 50-88.9 %w/w, where they provided clear appearance after dispersing in water. A high extract loading capacity was achieved by formulation composed of ethyl oleate in the presence of co-solvent or co-surfactant. The dissolution and stability of Passiflora foetida extract were shown to be best described by using vitexin as marker. It was shown that vitexin could be dissolved from the self-emulsifying liquids > extract > self-emulsifying granules > extract granules. Preparation of self-emulsifying granules by adsorption of self-emulsifying liquid on microcrystalline cellulose led to decreased vitexin dissolution but improved stability. In this study, the potential self-emulsifying liquid providing enhanced vitexin dissolution to the greatest extent was composed of 25% ethyl oleate/ 56.3 % Tween 80/ 18.8% propylene glycol. Its granules were also stable, i.e. vitexin remaining up to 95% after storage in refrigerated and at 25 °C conditions for 4 months.
